textproduct: Albany

WHAT HAS CHANGED

Increased snowfall amounts closer to and north of I-90, resulting in northward expansion of Winter Storm Warnings/Winter Weather Advisories.

KEY MESSAGES

1. Moderate to heavy snow develops between roughly 4 and 7 PM from west to east across the region, with heaviest snow now expected from slightly north of the I-90 corridor and points south/east. Moderate snow also expected across the southern Adirondacks and southern VT.

2. Precipitation develops early Sunday evening and may continue into Monday morning, likely beginning as a wintry mix (mostly freezing rain) before potentially ending as plain rain or rain/snow mix in higher elevations by Monday late morning into the early afternoon. The Monday morning commute will likely be impacted by the icy conditions in some locations.

3. Much colder with windy conditions and lake effect snow Monday night through at least the middle of next week.

DISCUSSION

KEY MESSAGE 1...

Bitterly cold afternoon transitions to a very snowy evening/night, as system currently tracking across MI moves east/southeast. Quite a bit of elevated convection noted on regional radar/satellite and lightning networks, reflecting the strong dynamics associated with this system.

We expect snow to develop from west to east across the area between 4 and 7 PM. Snowfall intensity will increase rapidly, with snowfall rates likely reaching 1-2"/hour shortly after snow onset within most of the warning area. The heaviest snow may last 2-3 hours, before decreasing in intensity toward and especially after midnight. Where the heaviest snowband lingers longest is where greatest amounts will be, which currently favors areas across the eastern Catskills to areas near or just south/west of the Capital Region, where localized amounts in excess of 8" will be possible. Elsewhere, generally 5-8" is expected within the warning area, with generally 3-6" within the advisory area, lowest across far northern Herkimer/Hamilton Counties and northern Warren/Washington Cos.

There is still a bit of uncertainty regarding the higher end amounts across the warning area, as model soundings suggest that after the initial burst of heavy snow where upward motion will be maximized through the dendritic growth zone, the best upward motion shifts underneath this layer fairly quickly toward and after midnight. This may allow snow to become more dense in consistency with slightly reduced accumulations, especially if a mid level dry slot accelerates more quickly than anticipated. Will have to watch this trend closely which could cause overall snowfall amounts to "underachieve" for areas south of I-90.

The very cold temperatures prior to, and during the snowfall will allow snow to accumulate on ground surfaces very quickly and efficiently, creating snow covered roadways and very slippery travel conditions overnight.

Although steadiest snow should taper off by mid morning Saturday, some pockets of light snow/snow showers may linger through midday associated with inverted trough extending from departing coastal wave. Additional very light accumulations could continue in some areas during this time.

KEY MESSAGE 2...

Potentially bitterly cold night for Saturday night, especially if skies clear out early given expected deep fresh snowpack. This could allow for temps to drop into the single digits above and slightly below zero (if not colder). This will then set the stage for a developing wintry mix (mainly freezing rain) Sunday evening and continuing overnight Sunday into Monday morning. Strong warm advection aloft allows temps to surge above freezing quickly, however shallow cold air will likely persist near the surface, particularly areas north of I-90. Widespread freezing rain, possibly mixed with sleet at the start, is expected to develop Sunday evening, generally between 6 and 10 PM from west to east. Antecedent very cold ground surfaces will allow for effective ice accretion on untreated ground surfaces Sunday evening/night, resulting in hazardous travel. In addition, freezing rain may continue through daybreak Monday in some sheltered areas mainly north of I-90, with flat ice accumulation potentially reaching as high as 0.25-0.35" in some areas. Again, will have to watch trends closely as this could result in some additional impacts including a few downed tree limbs/power outages should these ice amounts (or even greater) occur.

Freezing rain should eventually change to plain rain by late Monday morning, with rain then potentially mixing with snow later in the day as colder air aloft begins moving back into the region.

KEY MESSAGE 3...

Strong gusty winds, potentially heavy lake effect snow, and cold temperatures expected Tuesday into Wednesday.

As the aforementioned sfc low continues to track off to our northeast, it will continue to deepen below 980 mb as it becomes vertically stacked beneath an upper low. With a strong 1035 mb sfc high over the southern Plains, this will set up a strong pressure gradient across our area. The resulting 850 mb LLJ still looks to be on the order of 45-55kt, and with strong cold advection and boundary layer mixing this will translate to gusty winds at the sfc. Per the 00z ECMWF ensemble EFI values are >0.7 across much of our area, with a SOT between 0 and 1, which is a strong signal this far out for gusty winds. Much of our area will likely need wind advisories, with some targeted high wind warnings not out of the question. The best chance would be in the Berkshires, where the NBM is already showing 30-40% chances for wind gusts >58 mph Tuesday.

With storm W/NW flow and cold advection over the relatively warm Great Lakes, potentially heavy lake effect snow is also a concern Tuesday into Wednesday. While it is uncertain just how cold the airmass behind this next system will be, there is good consensus for 850 mb temperatures to reach or drop below -15C, which should allow for plenty of lake-induced instability. W/NW flow trajectories favor the southwestern ADKs and perhaps western Mohawk Valley, but very subtle changes in wind direction could shift the placement of the lake effect bands. NBM currently shows a 50-80% chance for the southern ADKs to see >6" of snow Tuesday into Wednesday, and given the tendency of the NBM to struggle with lake effect snow we would expect these probabilities to increase over the coming days. Best chance for lake effect snow is Tuesday into Wednesday, but there are signals that a clipper system and associated cold front could bring additional chances for snow showers towards the end of next week as well.

Finally, the combination of gusty winds and cold temperatures could lead to some below-zero wind chills Tuesday and Tuesday night for the high terrain areas. We remain in a cold pattern through the end of next week, with lows each night dropping into the single digits to teens, with some below-zero readings Wednesday and Thursday nights as our next cold front brings a reinforcing shot of cold air.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Through 00z Sunday...Flying conditions will quickly deteriorate this evening as a winter storm impacts the terminals. Conditions will be primarily IFR to LIFR, with VLIFR in the heaviest snow bands this evening at KALB/KPSF/KPOU. Snow will continue into early Saturday morning with IFR/LIFR conditions, with a gradual improvement expected by mid-morning to MVFR ceilings. Uncertainty remains in how long light snows will linger, so have hung on to PROB30 mentions for all terminals Saturday morning. Regardless, VFR conditions will return areawide late in the period for all terminals. Snow accumulations of around 6-10" for KPOU, 5-9" for KALB/KPSF and 4-6" for KGFL. Winds will be from the E/NE this evening, backing to N/NE Saturday morning with values remaining around or under 5 kts.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: High Operational Impact. Definite RA...FZRA. Monday: High Operational Impact. Breezy. Definite SHRA...RA. Monday Night: Moderate Operational Impact. Windy With Gusts To 33 kts. Chance of SHRA...SHSN. Tuesday: Moderate Operational Impact. Windy With Gusts To 39 kts. Chance of SHSN. Tuesday Night: Moderate Operational Impact. Windy With Gusts To 31 kts. Slight Chance of SHSN. Wednesday: Moderate Operational Impact. Breezy. Chance of SHSN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Winter Storm Warning until 1 PM EST Saturday for CTZ001-013. NY...Winter Storm Warning until 1 PM EST Saturday for NYZ038>041- 047>054-058>061-063>066-082. Winter Weather Advisory until 1 PM EST Saturday for NYZ032-033- 042-043-083-084. MA...Winter Storm Warning until 1 PM EST Saturday for MAZ001-025. VT...Winter Weather Advisory until 1 PM EST Saturday for VTZ013>015.